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Abstract:

A method for detecting a phase angle difference between a first periodic
measurement signal and a second periodic measurement signal, wherein, for
the purpose of determining a torque applied to a shaft, the two periodic
measurement signals describe a rotation of the shaft at an axial distance
from one another including superimposing a periodic auxiliary signal
which simulates a previously known rotational speed for the shaft on the
first periodic measurement signal in order to form a superimposition
signal, and determining the phase angle difference on the basis of the
superimposition signal and the second measurement signal.

Claims:

1. A sensor for emitting an electrical signal based on a travel to be
detected, comprising a housing which spans an interior space and an
exterior space, a signal generator which penetrates the housing from the
exterior space into the interior space and which has a travel sensor
element in the exterior space and a field signal generator element in the
interior space, wherein the travel sensor element is configured to rotate
the field signal generator element with respect to the housing on the
basis of the travel to be detected, an evaluation circuit for detecting a
physical field which is output by the field signal generator element, and
a moisture protection element for protecting a gap between the housing
and the signal generator against penetrating moisture.

2. The sensor as claimed in claim 1, wherein the moisture protection
element comprises a labyrinth which is configured to lengthen a flowpath
of the penetrating moisture in the gap.

3. The sensor as claimed in claim 2, wherein the labyrinth is embodied
from a first sleeve which is embodied on the signal generator, and a
second sleeve which is embodied on the housing and which engage one in
the other.

4. The sensor as claimed in claim 1, comprising a bypass element which is
configured to conduct the penetrating moisture past the gap.

5. The sensor as claimed in claim 4, wherein the bypass element is a
drainage channel which is embodied in at least one of the two sleeves.

6. The sensor as claimed in claim 5, wherein the corresponding other
sleeve has a projection which engages in the drainage channel.

7. The sensor as claimed in claim 3, wherein at least one of the sleeves
engages in a circumferential groove which is correspondingly embodied on
the housing or on the signal generator.

8. The sensor as claimed in claim 1, wherein the housing and/or the
signal generator are embodied conically running away from an inlet point
of the gap.

9. The sensor as claimed in claim 8, wherein the conical profile is
embodied on the inside and on the outside.

[0002] The invention relates to a sensor for emitting an electrical signal
on the basis of a travel to be detected, in particular of an angle.

BACKGROUND OF THE INVENTION

[0003] WO 2006/029 946 A1 incorporated by reference herein discloses an
angle sensor having a signal generator magnet and a measuring circuit
with evaluation electronics for evaluating an angular position of the
signal generator magnet. The signal generator magnet does not have any
direct mechanical connection to the measuring circuit, with the result
that from the point of view of the evaluation electronics the signal
generator magnet hovers above the measuring circuit.

SUMMARY OF THE INVENTION

[0004] An aspect of the invention aims to improve the known angle sensor.

[0005] According to one aspect of the invention, a sensor for emitting an
electrical signal based on a travel to be detected comprises a housing
which spans an interior space and an exterior space, a signal generator
which penetrates the housing from the exterior space into the interior
space and which has a travel sensor element in the exterior space and a
field signal generator element in the interior space, wherein the travel
sensor element is configured to rotate the field signal generator element
with respect to the housing on the basis of the travel to be detected, an
evaluation circuit for detecting a physical field which is output by the
field signal generator element, and a moisture protection element for
protecting a gap between the housing and the signal generator against
penetrating moisture.

[0006] The specified sensor is based on the idea that it could be used on
a vehicle for detecting a relative position of a wheel of the vehicle
with respect to its chassis. In this way, an active chassis control
system could be implemented with which the classic conflict of objectives
between a sporty and a comfortable adjustment of the chassis and
suspension could be resolved.

[0007] However, it becomes apparent here that such sensors are very
susceptible to faults and therefore have a relatively short service life.
Within the scope of the specified sensor it is recognized here that a
main cause of the short service life is the moisture penetrating into the
sensor which damages the evaluation circuit of the sensor and makes it
functionally incapable. This penetrating moisture is caused by the fact
that the sensor is mounted on the underside of the vehicle and is
subjected directly to dirt and moisture which is thrown up from the road.

[0008] The specified sensor is therefore based on the idea of protecting
said sensor and, in particular, its evaluation circuit against
penetrating moisture by a moisture protection element.

[0009] The moisture protection element can be embodied in any desired
fashion. In a particularly advantageous fashion, the moisture protection
element comprises a labyrinth which is configured to lengthen a flowpath
of the penetrating moisture in the gap. Such a labyrinth can be
implemented by means of simple geometric changes to the housing and/or
signal generator and therefore requires in principle no new elements,
with the result that the moisture protection element could be implemented
in the specified sensor in a cost-neutral fashion.

[0010] In one development of the specified sensor, the labyrinth is
embodied from a first sleeve which is embodied on the signal generator,
and a second sleeve which is embodied on the housing and which engage one
in the other. Two such sleeves would lengthen the abovementioned gap
between the housing and the signal generator in an axial fashion with the
result that the entry of the penetrating moisture into the interior space
is delayed to a high degree.

[0011] In another development, the specified sensor comprises a bypass
element which is configured to conduct the penetrating moisture past the
gap. In this way, the avoidance of the penetration of the moisture could
be improved further.

[0012] In a further development of the specified sensor, the bypass
element is a drainage channel which is embodied in at least one of the
two sleeves. This drainage channel can be embodied in a cost-neutral
fashion on the sleeves by means of simple geometric changes, without
additional technical elements being necessary. The drainage channel can,
for example, conduct the water circumferentially past the gap, wherein
the water would then drop down from the drainage channel underneath the
gap without penetrating said gap.

[0013] In one preferred development of the specified sensor, the
corresponding other sleeve has a projection which engages in the drainage
channel. In this way, the previously mentioned gap is lengthened even
further and the labyrinth effect is therefore enhanced further.

[0014] In order to enhance the labyrinth effect even further, at least one
of the two sleeves, but preferably both bushings, can engage respectively
in a circumferential groove which is correspondingly embodied on the
housing and/or on the signal generator.

[0015] In yet another development of the specified sensor, the housing
and/or the signal generator is embodied conically running away from an
inlet point of the gap. In this way, the quantity of moisture which can
potentially enter the gap at all is reduced.

[0016] It is particularly preferred to embody the conical profile here on
the inside and on the outside, with the result that moisture penetrating
the gap on the inside is conducted back again to the gap.

[0017] According to a further aspect of the invention, a vehicle comprises
one of the specified sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The properties, features and advantages of this invention which are
described above and the way in which they are achieved become clearer and
more clearly comprehensible in relation to the following description of
exemplary embodiments which are explained in more detail in relation to
the drawings, wherein:

[0019] FIG. 1 shows a schematic view of a vehicle with a chassis control
system,

[0020] FIG. 2 shows part of a CPS sensor,

[0021] FIG. 3 shows part of an alternative CPS sensor,

[0022] FIG. 4 shows part of a further alternative CPS sensor, and

[0023] FIG. 5 shows part of yet another CPS sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Identical technical elements are provided with identical reference
symbols in the figures and described only once.

[0025] Reference is made to FIG. 1 which shows, in a schematic view, a
vehicle 54 with a chassis control system 56.

[0026] Within the scope of this chassis control system 56, lifting
movements, pitching movements and rolling movements of a chassis 58 with
respect to a road (not illustrated further) on which wheels 60 of the
vehicle 54 roll in a positionally fixed fashion in a vertical axis 62 are
to be minimized in order to improve the driving properties of the vehicle
54 when travelling in a direction of travel 64.

[0027] For this purpose, the chassis control system has, in a fashion
known, for example, from DE 10 2005 060 173 A1, incorporated by reference
herein, a control device 66 which, in the present embodiment composed of
angle sensors 2 which are arranged on each wheel 60, receives rotational
angles 68 which describe a relative position of the corresponding wheel
60 with respect to the chassis 58. On the basis of the differences
between these rotational angles 68, the control device 66 determines
whether the chassis 58 is moving in the vertical axis 62, that is to say
is carrying out a lifting movement, or whether the chassis 58 is rolling
or pitching, and controls. In this case, the control device 66 calculates
a counter-movement, counteracting this lifting movement, rolling movement
and/or pitching movement, and controls, with suitable control signals 70,
active spring struts 72 which are arranged on the wheels 60, in order to
compensate this counter-movement with the chassis 6. For example, the
spring struts which are known from DE 101 22 542 B4, incorporated by
reference herein, can be used as active spring struts 72.

[0028] In order to take into account lifting movements, rolling movements
and/or pitching movements caused by the position of the road, for example
during cornering, a suitable setpoint value 74 can be fed to the control
device.

[0029] The angle sensors 2 are embodied in the present embodiment as
chassis position sensors 2, referred to below as CPS sensors 2. The
chassis position sensor measures a relative position of the chassis 58 of
the vehicle 2 with respect to its chassis and suspension or one of the
wheels 60. One of these CPS sensors 2 will be described in more detail
below with reference to FIGS. 2 to 5.

[0030] FIG. 2 illustrates an embodiment of the CPS sensor 2.

[0031] The CPS sensor 2 comprises a housing 4 which can be connected, for
example, in a positionally fixed fashion to the chassis 58 of the vehicle
54, and a signal generator 6 which detects the abovementioned relative
position of the chassis and suspension or wheel 60 of the vehicle 54 with
respect to the chassis 58 and therefore the housing 4. For this purpose,
the signal generator 6 is mounted in rotatable fashion with respect to
the housing 4.

[0032] The housing 4 comprises a housing wall 8 which separates an
interior space 10, in which an evaluation circuit (not illustrated
further) is accommodated, from an exterior space 12.

[0033] In addition, a first housing sleeve 14 and a second housing sleeve
16 which is arranged concentrically with respect to the latter project
axially from this housing wall, which housing sleeves 14, 16 together
form a housing groove 18 which lies radially between the latter. In
addition, a housing flange 20 projects concentrically inward from the
first housing sleeve 14, against which a third housing sleeve 22 adjoins
its radially inner side. In this third housing sleeve 22, a rotary
bearing 24 which is embodied, for example, as a sliding bearing is
secured.

[0034] The signal generator 6 comprises a lever 26 which is illustrated in
a cut-off form in FIG. 2 which can be moved, for example, by the wheel 60
and therefore can be rotated with respect to the housing 4. A first
signal generator sleeve 28 and a second signal generator sleeve 30 which
is arranged concentrically with respect to the latter project axially
from the lever 26, which signal generator sleeves 28, 30 form a signal
generator groove 32 radially between them. In this context, a signal
generator bead 31 is formed at the end of the first signal generator
sleeve 28 lying axially opposite the lever 26. A bushing 33, in which a
shaft 34 is held by means of a press fit, is arranged concentrically
within the two signal generator sleeves 28, 30. A field signal generator
element in the form of a magnet 36 is held in a positionally fixed
fashion with respect to the shaft 34 at the end lying axially opposite
the lever.

[0035] By virtue of the design mentioned above, the magnet 36 can be
rotated by means of the shaft 34 with the lever 26 with respect to the
housing 4 which is arranged in a positionally fixed fashion with respect
to the chassis of the vehicle. In this context, the housing 4 and the
signal generator 6 are arranged axially with respect to one another in
such a way that the first signal generator sleeve 28 engages axially in
the housing groove 18, the second housing sleeve 14 engages axially in
the signal generator groove 32, with the result that a labyrinth-like gap
37 is formed between the housing 4 and the signal generator 6. The shaft
34 carries out here the movement of the lever 26, arranged in the
exterior space 12, into the interior space 10 with respect to the magnet
36. The latter emits a physical field, in the form of a magnetic field,
which changes as a function of the position of the lever 26 and therefore
of the magnet 36, which magnetic field is sensed by the evaluation
circuit (not illustrated further) and, for example for the determination
of the relative position, is evaluated in a manner known per se.

[0036] In order to detect the relative position of the chassis and
suspension with respect to the chassis, the CPS sensor 2 must be
disadvantageously arranged on an underfloor side of the vehicle at which
it is subjected to a comparatively large amount of penetrating moisture
38. If this moisture 38 were to penetrate the interior space 10 of the
housing 4, it could damage the evaluation circuit (not illustrated
further) and make the CPS sensor 2 functionally incapable. For this
reason, the labyrinth-like gap 37 is embodied, which gap 37 increases the
travel for the moisture 38 and therefore lengthens the time by which the
moisture can reach the evaluation circuit.

[0037] In addition, the signal generator bead 31 forms, together with the
lever 26 and the first signal generator sleeve 28, a further moisture
protection element which is formed as a bypass. Said bypass is embodied
as a drainage channel 40 which runs on the radial outerside of the signal
generator sleeve 28 and which collects the moisture which penetrates from
the outer side 12 and conducts it circumferentially around the shaft 34
past the labyrinth-like gap 37 on the radial outer side of the signal
generator sleeve 28, with the result that the moisture cannot even
penetrate said gap 37.

[0038] As yet a further moisture protection element, it is possible, in
the present embodiment, to arrange a seal in the form of a Y seal 42
radially between the shaft 34 and the second housing sleeve 14, which
seal seals off the interior space 10 of the housing 4 physically with
respect to the penetrating moisture.

[0039] FIG. 3 illustrates part of an alternative CPS sensor 2. This
alternative CPS sensor 2 only comprises the second housing sleeve 16 and
the first signal generator sleeve 28 between which the labyrinth-like gap
37 is embodied.

[0040] For this purpose, in the second signal generator sleeve 16 a
further drainage channel 40 is embodied, into which a projection 44
projects radially in the present embodiment. Although this projection 44
requires an undercut 46 which has to be manufactured in a costly fashion,
the labyrinth-like gap 37 is nevertheless increased further by the
projection 44.

[0041] FIG. 4 shows part of a further alternative CPS sensor 2. The lever
26 cannot be seen on the signal generator in FIG. 4. However, instead,
FIG. 4 shows the evaluation circuit which is provided with the reference
symbol 48. Electrical contacts in the form of what are referred to as
pressfits 50, by means of which the evaluation circuit 48 can be
connected to a superordinate control device, such as, for example, an
engine controller of the vehicle, project from said evaluation circuit
48. Only one of these pressfits 50 is provided with a reference symbol in
FIG. 4.

[0042] In FIG. 4, the signal generator bead 31 is embodied in a conical
fashion and projects over an input 52 of the labyrinth-like gap 37. In
this way, the possibility of moisture penetrating into the labyrinth-like
gap 37 is reduced further.

[0043] FIG. 5 illustrates part of yet another CPS sensor 2. In this CPS
sensor 2, the first signal generator sleeve 28 is embodied running
conically from the inlet point 52 of the labyrinth-like gap 37 to the
lever 26. This conical shape is embodied here within the gap 37 and
toward the exterior space 12, with the result that moisture is conducted
away from the inlet point 52 of the labyrinth-like gap 37 at the exterior
space, and is conducted to the inlet point 52 within the labyrinth-like
gap 38.